A carbon fber reinforced thermoplastic (CFRTP) was irradiated with a high energy electron-beam. As a result, the ten�sile strength of high-density polyethylene (HDPE)-based CFRTPs was signifcantly improved by gradually increasing the electron-beam dose. It was confrmed that the adhesion between CF and HDPE was improved and the surface properties of CF and HDPE were readily modifed by electron-beam. It was verifed from spectroscopic analysis that various oxygen�containing functional groups were formed on the surface of CF and HDPE by irradiation and we believe that strong attrac�tive interactions took place among these functional groups at the interface of CFs and HDPE. Finally, it was conclusive that electron-beam irradiation provided two main efects on CFRTPs. One was cross-linking of thermoplastic resin for efcient load transfer from resin to CF and the other was formation of surface functional group and attractive interaction of these functional groups at the interface of fber and matrix. These two efects showed synergetic contribution to enhance the mechanical properties of CFRTP.